Heretofore, carbamates (urethane compounds) such as alkyl carbamates have been useful organic compounds as an industrial raw material having a wide variety of use, including a raw material for medical and pharmaceutical products, agrochemicals, etc.; a raw material for various fine chemicals; and also as an analysis reagent for alcohols.
Also, various examinations have recently been conducted on use of such alkylcarbamate as a raw material for phosgene-free isocyanate production.
Isocyanate is an organic compound containing an isocyanate group, used widely as a raw material for polyurethane, and industrially, produced by reaction between amine and phosgene (phosgene method).
However, phosgene is highly toxic and corrosive, and its handling is troublesome. Therefore, recently, as an economic method of isocyanate production that can replace the phosgene method has been proposed: in the method, carbamate is produced by reaction between amine, urea or carbamic acid ester, and alcohol, and thereafter, isocyanate is produced by thermal decomposition of the obtained carbamate.
As an example of such a carbamate production method, Example 11 of Patent Document 1 below has proposed obtaining 2,4-bis-(n-hexoxycarbonyl-amino)-toluene by reaction between diaminotoluene, urea, and n-hexanol in the presence of a Lewis acid catalyst.